Machine tool



Jan. 4, 1944.. w. F. RIDGWAY 2,338,599

MACHINE TOOL Filed Nov. 8, 1941 15 A3 /5 J4 4 J2 T-rOQ N my;

Patented Jan. ,4, 1944 MACHINE 'roor.

William' F. Ridgway, Rockford, 111., assignor to" The Ingcrsoll MillingMachine Company, Rockford, Ill., a corporation of Illinois ApplicationNovember 8,1941, Serial No. 418,297

2 Claims.

This invention relates to machine tools having a power rotated elementsuch as a cutter spindle or a work support which must be driven atdifferent peripheral speeds depending on the character of the work andcutting materials. To adjust the power drive for a change in cutter orwork diameter, several time consuming operations are required. Forexample, when the cutter size is changed, the common practice is toselect the proper cutting speed'for the given cutting and workmaterials, determine the spindle speed required to produce this cuttingspeed either by calculation Or by reference to charts, and then adjustthe spindle driver speed accordingly.

The present invention aims to simplify the operations of conditioning amachine for changes in cutter or work diameter.

A more detailed object is to provide an electrically operated mechanismresponsive to the speed of the rotary machine element and operable toindicate the effective peripheral speed while the rotational speed ofthe driving mechanism is being adjusted.

The invention also resides in the novel character of the mechanismemployed in carrying out the foregoin objects- Other objects andadvantages of the invention will become apparerit from the followingdetailed description taken in connection with the accompanyingdrawingwhich is a schematic view and wiring diagram of amachine tool equippedwith a speed adjusting mechanism embodying the present invention.

In the drawing, the invention is illustrated as a means for facilitatingthe adaptation of a milling machine for cutters of diiferent sizes andwork and cutting materials of different diameters. This involvesadjusting the speed of the cutter spindle l to produce the desiredcutting speed which, in the case of a face milling cutter 5, is theperipheral speed at the radius. of engagement of the cutter teeth 6 withthe work I. The work may be mounted on a table 8 moved along ways 9 tofeed the work to the cutter. The latter is detachably mounted on one endof the spindle which herein is driven through appropriate speed changeand reduction gearing ID by an electric motor I l preferably of thedirect current type. The motor speed may be adjusted to give the desiredspindle speed by selectively positioning a manually operable knob [2 ofa rheostat [3 having its resistance l4 interposed in the field circuit Iof the motor.

In accordance with the present invention,

generator output to an indicating meter 20 in ratios for producingperipheral speed indications corresponding to different cutterdiameters. The meter is any voltage responsive device of the DArsonvaltype and preferably is an ordinary voltmeter having a pointer 2icoacting with a scale 22 which reads in terms of peripheral speed of thecutter, that is, feet per minute. A second scale 22 may be provided onthe meter and used when gearing Ill is shifted to a lower drive ratio.

Apportioning of the voltage is effected in the present instance by apotentiometer 23 having a resistance element 24 connected to onegenerator terminal by a conductor 25 and to a conductor 26 connectingthe other generator terminal to the winding 21 of the voltmeter. Theresistance is engaged by a wiper 28 connected to the other windingterminal and movable across the resistance by turning a knob 28. Apointer 32 on the latter coacts with a stationary scale 30 readable ininches of cutter diameter. It will be observed that only the voltagedrop between the terminal 3i and the wiper 28 is applied to the meter.The resistance is so proportioned that when the pointer is positioned at8," the meter will indicate the peripheral speed of an eight inchcutter. At the same spindle speed and with the potentiometer set at 12,the voltmeter would indicate the cutting speed for a twelve inch cutter.

The procedure of conditioning the millingmachine for operation with acutter of given diameter, for example, six inches, with certain cuttingand work materials is as follows: The knob 29 is first set with thepointer registerin with the number 6 on the scale 30. The motor H isthen started and its speed is adjusted by means of the rheostat l3 untilthe meter 20 registers the cutting speed desired for the particularcombination of work and cutting materials being used. If, with the sameset-up the cutter is changed to one of, say, a fourteen inch diameter,the potentiometer setting is changed to 14, thereby increasing thevoltage applied to the meter. Then, the rheostat I3 is adjusted todecrease the spindle speed until the desired cutting speed is indicatedby the meter.

I claim as my invention:

1. In a machine tool having a rotary spindleadapted to support cuttersof diflerent efiective diameters and power driving means for rotatingthe spindle at selectively variable speeds, the combination of mechanismdriven in unison with said spindle to provide a voltage proportional inmagnitude to the spindle speed, a meter responsive to said voltage andreadable in terms of peripheral speed of cutters mountable on saidspindle, a manually operable member selectively adjustable to differentpositions corresponding to difler ent diameters of cutters to be mountedon said spindle, and means associated with said member and operable toapportion said voltage as applied to said meter and cause the latter toindicate the peripheral speed of a cutter of the diameter selected bythe setting of said member.

2. In a machine tool having a rotary spindle adapted to support cuttersof different eflective diameters and power driving means for rotatingthereof to apportion said voltage as applied to said meter in accordancewith the selected cutter diameter and cause the meter to indicate theperipheral speed 01 selected cutter.

WILIJAM F. RIDGWAY.

